One battlefield lesson seemingly never learned is how fundamentally wrong it is to be anything less than fully open and truthful about what is taking place in the war zone.

Apparently, the public scorn and congressional wrath the Army suffered for lying about the actions of Cpl. Pat Tillman and Pfc. Jessica Lynch were not enough to convince some Pentagon leaders that it is folly to attempt to manipulate public perceptions about the war effort.

Earlier this month on Capitol Hill, a Pentagon lawyer halted a classified briefing on what arguably is the most important mission in the war in Iraq — training Iraqi security forces — by invoking a new Defense Department policy banning testimony or briefings by troops in paygrades below O-6. The ban applies to midlevel and junior troops if their remarks would be part of the public record, except in certain cases where they would be “deemed appropriate” by the Pentagon.

Though midlevel and junior troops are training Iraqis and deeply knowledgeable about that effort, Pentagon leaders for some reason did not want them to share their views with the House Armed Services oversight and investigations subcommittee.

The new policy’s author, Assistant Defense Secretary Robert Wilkie, said the policy — which he described as negotiable — was adopted to better manage the great number of requests for Capitol Hill appearances by defense personnel.

He also said, in a moment of stunning condescension, that officials were “trying to take care of our junior folks,” who he said otherwise might have to engage in “the back and forth of policy debates” with the likes of professors or outside witnesses.

Wilkie’s official explanation aside, it is hard not to suspect that the new policy is really intended to stifle testimony that might conflict with Pentagon portrayals of conditions on the ground. Certainly, DoD has a track record of inflating the number of Iraqi security forces trained and fully mission capable.

How ironic and wrong it is that troops risking their lives to establish democracy in Iraq are being denied rights of free speech to inform Congress and the nation about those efforts.

Lawmakers were properly outraged and say the new policy won’t stand — and it shouldn’t. The nation is in the midst of a critical debate on whether to continue to spend its blood and treasure on the war in Iraq, and progress in training Iraqi security forces is a central issue.

Congress must have unobstructed access to any service member it deems necessary to call on, from a private to a four-star general, in the quest to get to the truth about the war.

Meanwhile, the Iraqi government has also taken a step that defies the principles of democracy — banning media photography of the aftermath of bomb attacks. Iraqi officials claim the ban is meant to keep the press from tainting evidence, but it’s really an attempt to control the public image of the situation in Iraq. It’s as if they believe that if there are no pictures of another car bombing, no one will know that one occurred.

It won’t work. The truth cannot be contained.

If official media are not allowed to photograph the mayhem, unofficial media will fill the void, as was the case at the hanging of Saddam Hussein. Insurgents routinely record the death and chaos caused by their bombs and use the Internet to get those images to major media outlets.

Their version of events will not be constrained by a government crackdown.

By contrast, most Western media, which strive to present a balanced account of war-zone conditions while self-censoring to withhold the most gruesome images, won’t be able to photograph bomb scenes until they’ve been cleaned up to present a sanitized view.

An unfettered press, free to shine a light on the good and bad, is an inherent element of a true democracy.

Anything less cedes power from the people to the government — and that is absolutely the wrong direction.